Inside the PowerPC 970

Part II: The Execution Core

Conclusions

By way of conclusion, I should enumerate the important information that I
don't yet have access to:

Confirmation of the Altivec unit latencies

Confirmation of the identities of the new pipeline stages in the vector
execution phase and in the common fetch/decode phase.

L1 and L2 cache latencies

Of the above three items, I'm fairly certain that my speculation on the first
two is correct. As for the last item, the cache latencies, this is important
information that we'll all just have to wait for.

Regarding the future of the 970, much will depend on how aggressive IBM is in
ramping up the clock speed and adding new features. When will we see an on-die
memory controller? Will we see a version with more cache? Will they add support
for an L3 cache? All of these are questions that only time will answer.

I do hold out some hope that we'll see the 970 scale just north of 2GHz
fairly soon, based on the fact that IBM has just announced that its top-end
Power4 server is now at 1.7GHz. In my first article, I mentioned the fact that
the Power4 is built for reliability, not speed; hence it has thicker gate oxides
that spell lower clock speeds. The 970 is meant to be faster and less reliable,
so just based on the difference in the gate oxide thickness alone I would expect
the top-end 970 to bump up against 2GHz. And when you factor in the 970's much
smaller die size, even more MHz can be added to the top-end estimate.

Finally, as I've mentioned a number of times in this article and in other
places, the 970 is made for SMP designs. So I look for the top-end 970 machines
from both Apple and IBM to be dual-processor right out of the gate. And in fact,
I would expect that machines with four processors and more are in the works from
both companies.

On the IBM side, I think the 970 will make a great Linux platform, especially
for content creation companies that are currently replacing their expensive
64-bit *NIX workstations and rendering machines with commodity x86-based Linux
systems. If IBM can keep the prices of its 970-based Linux boxes competitive,
they could see their systems gain traction in many of the places that
Linux-based PC systems are starting to enter.

Finally, turning once again to Apple's use of the 970, I believe that Apple
is poised for a huge overhaul of its hardware line based on this processor and a
renewed relationship with IBM. I'm finally convinced that Apple's days of
wandering in the wilderness with Motorola are over, and that personal computer
users will be able to see the Mac as a real option again in terms of desktop,
and not just portable, performance.

As with all things Apple, though, the big question is price. Will Apple drop
its margins drastically and sell these machines at a competitive price point in
order to increase market share, or will it continue to price itself into the
increasingly non-existent luxury/lifestyle computing niche? I'm hoping for the
former, because I'd love to give my TiBook and iPod some company with a
970-based PowerMac. If the answer is the latter, though, my Apple products will
likely find themselves interoperating with an x86-64 Windows box.

Bibliography

In addition to the bibliographical entries for the previous article, see also
the following documents: